I played around with the Multiplexer for an evening trying to get it to work with both a Distributed Hashtable and a 'Normal' Channel (using UDP) and could not get it going. I have no doubt it is something I was setting up wrong which is why I wanted to check with the group.

STACK_FILE must be on your classpath; JGroups provides a file named stacks.xml in its distributable jar. You can use this file or create your own with customized stacks. STACK_NAME refers to the stack within STACK_FILE.